Amplifier connection



Aug. 10 1926.

. G. RESPONDEK AMPLIFIER-CONNECTION Filed July. l5 1924 Invshnrff Gevfg ReSpondeK:

n Hi8 Abtcned' Patented Aug. 10, i926.

UNITE rafts GEORG RESPCNDEK, OF BERLIN-H1LENSEE, GEBMNY, ASSGNOR T0 GENERIL TRIO COMPANY, A CORPORATION 0F NEU] YQRE.

AMPLFER CONNECTON.

- application "tied July 15, i924. Serial No. 228.200, and in Germany September 12 Mv present invention relates to amplifier connections adapted for use in 4 long distance telephone lines.

In the connection oi the coil circuits in 5 a duplex telephone circuit with intermediate amplifiers the :im-arent resistance of the two lines connected by the intermediate amplifiers or the, apparent resistance of each of the lines .and the artificial reproduction oilv l' the same must bc carefully cqualizcd with reference to frequency. li' this is not done back coupiing takes place so that a disturbing Whistling of the anipliiier is heard, Whenever a certain degree of ainplii'ication is l vexceeded.

It is not possible in practice to obtain the y equalization between the apparent resistance of the coil circuits and their artiticial reproduction for all frequencies. As shown by theory` and practice, `the diilicultiesv of reproduction are especially great in the neighborhood of the natural frequency of the coil circuits.

The object ot' my present invention, which is an improvement over that described in a copending application of Friedrich Gchrts, Serial No. 661,785), iilcd September l0, 1923, is to provide means whereby the. diiiiculties of producing theI desired equalization are reduced to a minimum. lnicarrying my invention into ellcct, .l provide in the amplifier connections suitable connecting imped ancesI which are automatically variable in accordance with the direction of conversation in such a way that the development of a disturbing auto excitation is avoided, especially within the range of frequencies in the neighborhood of the natural frequency of the coil connections. The means for obtaining such results may be a choke coil the inductance of which is kept small by -premagnetization which may be lcompensated by a counter magnetization which becomes effective at .the moment talking is Started in the -other direction. The counter magnetization may be obtained by means of a direction am liier or similar rectifying arrangement. AVhile a choke coil is the preferred form' of impedance, variablev conn densers or resistances may also be used if desired.

The novel features which i believe to be characteristic of myfinvention are set forth With particularity in the appended claims..

5 My invention itself7 however, both as to its vnetization of the core o organization and method of operation will best be und 'stood by reference to the ich lowing description taken in connection with the acconxrmnying drawing in which i have indicated diagranunatically one Way v-Ihereby niy invention may be carried into eilect.

I have indicated in the drawing a duplern connection for two lines ii, and F2 to each of which is connected an nrtitieial line Ki. and K12. For cach talking' direction there is provided van amplifying tube Vkand V2, and there is also connected` to each line e. direction. amplifier P.; and R2. 'The choke coil, Drl, which is inserted in the line if; V1 F2 may have its initial'magnetization adjusted by means of a separate source ot current and a special Winding. This however is not neccssarv the initial magno@ ization may be provided by means ot 'the current'in the output circuit oi direction '753 ampliiierRl, which is supplied to the ivi ing T1. The talking currents arriving over -the line F1 are supplied on the 'one hami to the grid circuit of ampiiiier "(1 and other hand to the eoii l in the grid of direction amplifier R1. The tr" rents are ampliiied by the dinH fier El and the amplified ciu therefrom to 'the Windin sired manner. .it the lier V1 transmits the :mi rents through the windi coil Dr1 to the outgoing; line F2. talking:r currents now produce at the same time in conjunction with the current Sup- `lied'to Winding T] a change in the choking imits of the coli `tor the criticai Jfrequency range.

In the copending application ci' Friedrich Gehrts referred to above, the input circuits of the direction amplifiers were connected across the telephone lines. Because of this, the direction ampiiiers were also affected by the ampliied currents and a back coupling was produced which might cause a dis turbing whistling. Choke coils l) and conh densers C were provided for the elimination of such eifectsf In the present case` this diiiiculty. is avoided by connecting, the grid circuits oi:

.the direction amplitiers in series with the telephone lines. The grid coils may be con nectcd to the equalization connection of the telephoneline or the input/circuits of the direction amplifiers may themselves be formed as equalizingJ connections A lll'1 and A Uf, as indicated., or U2 and A Ug, as shown by dotted lines.

By reason ot this connection, the talking current acts on the grid of direction amplifier lit-1 in the 'same manner thatdt acts on the grid or". speech amplifier V1 so that the connection is tree from any back coupling and the choiiecoils D are no longer essential.

The operation of thedirection amplifier RZ, the speech amplifier V2 and coil Dr2 for speech current comingfrom 'the line F2 is the same as that described for the corre spending' elements which are actuated by speech comingl from the line F1.

Tha-t i claim as neu7 and desire to secure by Letters Patent oiv the `United States, is:

1. The combination in a duplex telephone amplifier system of an incoming line and an outgoing line, an amplifier for amplifying a portion of the currents received over the in.- coming line and delivering amplified currents to the outgoing 'line7 an impedance connected in the outgoing; line, a second amplifier having its input circuit connected. to the incoming line by an equalizing connection so that it will be actuated only by incoming currents and means for controlling the vaine ot said impedance by the current in the output circuit of the second. amplifica 2l ''.ihe coinbinatioii ina duplex telephone amplifier ot an incoming line7 an artificial line connected to the end of said incoming line7 an outgoing line, means 'for amplifying portion of the currents received over the incoming iine delivering amplified currents to the outgoing line.an impedance connected in the outgoing line, an amplifier having a coil in its input circuit connected in series relation to Said incoming line and artificial line, and means controlled by the current in tlie output circuit of said amplifier tor varying the value of said impedance.

3. The combination in a duplex telephone amplifier system of a pair of amplifiers having their input circuits connected to a telephone line by equalizing connections so that they Will be actuated only by currents received oversaid line, one ot said amplifiers being connected to deliver amplified currents to an outgoingline and the other of said amplifiers being connected to control the impedance of the outgoing line.

4. The combination in a duplex telephoneamplitier system of an incoming line and an outgoing line, an amplifier Yfor amplifying a portion otl the currents received over the incoming line and delivering amplified currents to 'the outgoing line7 an iron core inductance connected in the outgoing .line and a second aniplificr having its input circuit connected to the incomingl line and having in its` output circuit a magnetizing Winding surrounding the core of said inductance, said amplifier being so adjusted that the normal current in its output circuit produces a prcdetern'iincd desired magnetization of said core and the modified current in the output circuit when speech current received over the incoming line ln'otlruee4 u change inthe magnetization or the core and thereby varies the value ot' the inductance in a desired manner.

in witness "whereof, l hare hereunto my hand this llth day ol April, 1924.

GEORG RESPONDER. 

